TWI659217B - Wireless passive strain sensor - Google Patents

Abstract

The invention discloses a wireless passive strain sensor, which comprises an outer coil support, a reading inductance coil, a capacitor patch, an inner coil support and a sensing inductance coil. The shaft passes through the outer coil support. The reading inductance coil is arranged on the outer coil support. The capacitor patch is arranged on the rotating shaft. The inner coil bracket is located inside the outer coil bracket, and the inner coil bracket is disposed on the rotating shaft. The sensing inductor is disposed on the inner coil support, and the sensing inductor is connected to a capacitor patch.

Description

Wireless passive strain sensor

The present invention relates to a strain sensor, and more particularly to a wireless passive strain sensor for sensing a strain amount of a rotating shaft.

Generally, if a load is to be measured on a dynamically rotating shaft, a sensor is usually placed on the shaft. However, placing a sensor on the shaft requires the installation of a battery or a wireless transmission module, which will take up additional space, or the wiring will entangle the shaft during rotation, or the shaft will need to be processed, and the above methods will be due to the placement The sensor affects the rotation of the rotating shaft and affects the measurement result.

In view of the above-mentioned conventional problems, an object of the present invention is to provide a wireless passive strain sensor to solve the problems in the conventional technology.

Based on the above purpose, the present invention provides a wireless passive strain sensor, which is suitable for measuring the strain of a rotating shaft. The wireless passive strain sensor includes an outer coil bracket, a reading inductor coil, a capacitor patch, an inner coil bracket, and a sensor. Measure the inductance coil. The shaft passes through the outer coil support. The reading inductance coil is wound on the outer coil support. The capacitor patch is arranged on the rotating shaft. The inner coil bracket is located inside the outer coil bracket, and the inner coil bracket is sleeved on the rotating shaft. The sensing inductor is wound on the inner coil support, and the sensing inductor is connected to a capacitor patch.

Preferably, the reading inductor can be connected to an antenna analyzer.

Preferably, the antenna analyzer can scan and read the resonance frequency of the inductive coil corresponding to the inductive coil.

Preferably, the antenna analyzer can be connected to a computer, and the computer receives the resonance frequency, generates a resonance frequency result according to the resonance frequency, and displays the resonance frequency result.

Preferably, a bearing structure may be provided between the outer coil support and the inner coil support.

Preferably, the bearing structure may include a plurality of ball bearings.

Preferably, the ball bearing may be a polyoxymethylene plastic bearing.

Preferably, the capacitor patch can be a finger-type capacitor, one end of the finger-type capacitor is connected to one end of the sensing inductor, and the other end of the finger-type capacitor is connected to the other end of the sensing inductor.

Preferably, the capacitor patch may be a flexible patch.

Preferably, the included angle between the capacitor patch and the axis of the rotating shaft may be 45 degrees.

As mentioned above, the wireless passive strain sensor of the present invention has the following advantages:

1. Wireless transmission: The reading inductance coil is supported by the outer coil support, which can be measured on the rotating shaft without tangling.

2. Small space requirement: The sensing end is composed of the sensing inductor and the inner coil bracket. It does not need to install a battery module, which effectively reduces the occupied space.

3. Easy to operate: no tedious operations such as battery module replacement and shaft removal.

4. The shaft does not need to be processed: the shaft does not need to be lengthened, changed in material or shape.

5. Patch flexibility: can be attached to the surface of moderately curved objects.

6. Can be measured immediately.

100‧‧‧Wireless passive strain sensor

110‧‧‧Outer coil bracket

120‧‧‧Read inductive coil

130‧‧‧Capacitive patch

140‧‧‧Inside coil bracket

150‧‧‧ sensing inductor

160‧‧‧ball bearing

200‧‧‧ shaft

300‧‧‧ Antenna Analyzer

400‧‧‧ computer

FIG. 1 is a first schematic diagram of the wireless passive strain sensor of the present invention.

FIG. 2 is a second schematic diagram of the wireless passive strain sensor of the present invention.

FIG. 3 is a first schematic diagram of a capacitive patch of the wireless passive strain sensor of the present invention.

FIG. 4 is a second schematic diagram of a capacitive patch of the wireless passive strain sensor of the present invention.

In order to better understand the features, contents and advantages of the present invention and the effects that can be achieved, the present invention is described in detail with the drawings in the form of examples, and the main purpose of the drawings is only The use of illustrations and auxiliary descriptions may not be the actual proportions and precise configurations after the implementation of the present invention, so the accompanying drawings should not be interpreted and limited to the scope of rights of the present invention in actual implementation.

The advantages, features, and technical methods of the present invention will be described in more detail with reference to the exemplary embodiments and the accompanying drawings for easier understanding, and the present invention may be implemented in different forms, so it should not be understood to be limited to this The embodiments described herein, on the contrary, to those having ordinary knowledge in the technical field, the embodiments provided will make this disclosure more thoroughly and comprehensively and completely convey the scope of the invention, and the invention will only be appended As defined by the scope of patent applications.

Please refer to Figures 1 to 4; Figure 1 is a first schematic diagram of the wireless passive strain sensor of the present invention; Figure 2 is a second schematic diagram of the wireless passive strain sensor of the present invention; and Figure 3 is a FIG. 4 is a first schematic diagram of a capacitive patch of the wireless passive strain sensor of the present invention; FIG. 4 is a second schematic diagram of a capacitive patch of the wireless passive strain sensor of the present invention. As shown in the figure, the wireless passive strain sensor 100 of the present invention is suitable for measuring the strain of the rotating shaft 200. The wireless passive strain sensor 100 includes an outer coil bracket 110, a read inductor coil 120, a capacitor patch 130, and an inner side. The coil holder 140 and the sensing inductor 150.

Continuing, the aforementioned outer coil support 110 is passed through the rotation shaft 200 but is not connected. The reading inductance coil 120 is wound around the outer coil support 110.

The capacitor patch 130 is mounted on the rotating shaft 200.

The inner coil bracket 140 is located inside the outer coil bracket 110 but is not directly connected, and the inner coil bracket 140 is sleeved on the rotating shaft 200. The sensing inductor 150 is wound around the inner coil holder 140, and the sensing inductor 150 is connected to the capacitor patch 130.

In more detail, the wireless passive strain sensor 100 of the present invention is an inductive capacitor loop type strain sensor. Its operating principle is that the inductance and capacitance circuit is strained to change the resonance frequency of the circuit, and the change of the resonance frequency can be The capacitance patch 130 is changed due to the deformation of the rotation of the rotating shaft 200. The capacitance patch 130 is connected to the sensing inductor 150, and then the sensing inductor 150 and the reading inductor 120 perform wireless transmission.

The configuration of the inner sensing inductor 150, the outer reading inductor 120, and the capacitor patch 130 is such that the sensing end formed by the inner coil bracket 140 and the sensing inductor 150 is mounted on the rotating shaft 200 as a whole. The electrodes are fabricated on a flexible substrate to form a capacitor patch 130 and adhered to the surface of the shaft 200, and the sensing inductor 150 is wound in a spiral manner on the inner coil bracket 140 and connected to the capacitor patch 130 array to form an inductor and capacitor. Circuit; the outer coil support 110 does not have any contact with the shaft 200, but can be connected to the housing of the body with the shaft 200 (for example only, and not limited to this), and surrounds the inner coil with a slightly larger diameter than the shaft 200 The holder 140 and the reading inductance coil 120 wound on the outer coil holder 110 in a spiral manner wirelessly read the sensing inductance coil 150 to constitute a wireless transmission module.

Wherein, when the rotating shaft 200 is a metal shaft, the sensing result of the sensing inductor 150 may be disturbed. Therefore, the present invention only winds the sensing inductor 150 around the inner coil bracket which is close-fit with the rotating shaft 200. In 140, the distance between the sensing coil 150 and the rotating shaft 200 is propped up by the inner coil bracket 140, so as to avoid interference.

Further, the reading inductance coil 120 may be connected to the antenna analyzer 300, and the antenna analyzer may be portable; further, the antenna analyzer 300 may scan and read the sensing inductance coil 150 wirelessly to the sensing inductance coil 150. More specifically, the antenna analyzer 300 can be connected to the computer 400, and the computer 400 receives the resonance frequency, generates a resonance frequency result according to the resonance frequency, and displays the resonance frequency result.

In addition, a bearing structure may be provided between the outer coil support 110 and the inner coil support 140; further, the bearing structure may include a plurality of ball bearings 160. The ball bearing 160 may be a polyoxymethylene plastic bearing.

According to the above, when the wireless passive strain sensor 100 of the present invention is set up, in order to prevent the sensing inductor 150 and the reading inductor 120 from being eccentric, a ball bearing 160 is introduced to fix the sensing inductor 150 and the reading. Taking the center distance between the inductor coils 120, the ball bearing size can preferably use 6805 (inner diameter 25mm, outer diameter 37mm) to achieve the effect of tightly fitting the inner coil bracket 140 and the outer coil bracket 110, because the aforementioned metal material is mentioned It will affect the signal transmission capacity, so the outer ring of the bearing structure and the ball bearing 160 inside are made of polyoxymethylene plastic (POM) plastic, which has a hard texture and is the most plastic that can withstand lateral loads. The speed was 980 rpm. The measurement platform for scanning the resonance frequency and display is connected to the DuPont line to read the inductance coil 120, and then the DuPont line is clamped by the antenna analyzer 300 to scan the resonance frequency. Finally, the computer 400 is connected to display the resonance frequency result.

The capacitor patch 130 described above may be an interdigital capacitor. One end of the interdigital capacitor is connected to one end of the sensing inductor 150, and the other end of the interdigital capacitor is connected to the other end of the sensing inductor 150. The capacitor patch 130 may be a flexible patch, and the included angle between the capacitor patch 130 and the axis of the rotation shaft 200 is preferably 45 degrees.

Among them, the design of the interdigital capacitor uses the theoretical model proposed by Rui Igreja and CJDias in 2004. The geometric design of the electrode is shown in Figure 3. W is the electrode width, G is the electrode spacing, L _o is the electrode length overlapping each other, and the positive and negative electrodes are connected to + V / -V, respectively. The interdigitated capacitor cross-section is shown in Figure 3. This design is based on the fact that the electrode width is much larger than the electrode thickness, so the effect of thickness is not considered. And because this design is a periodic structure, a parameter λ can be introduced as the length of the periodic structure, and the metallization ratio η can be calculated by using the proportion of the electrode, which can be calculated as formula (1) and ( 2): λ = 2 ( W + G ) (1)

There is a zero potential between the positive and negative electrodes, and due to the periodicity and symmetry of its structure, the zero potential will be exactly at the center between the two electrodes (as shown by the dotted line in Figure 4). Based on this characteristic, the equivalent circuit model of the capacitor can be derived as shown in Figure 4. C _E and C _I are the equivalent capacitances of the outside and inside, respectively. The total capacitance value of the finger-type capacitor can be calculated as formula (3 ), N is the total number of electrodes (must be an even number and greater than 3).

For example, the total capacitance value can be obtained through a series of conformal mapping techniques and complement operations, where (h is the dielectric thickness between the electrodes) is a geometric parameter of the cross-section ratio of the electrode, which will affect the equivalent capacitance of the outside and inside. The calculation of the final capacitance value must also be considered simultaneously if the use of multilayer materials will affect the capacitance value. The multilayer material on the left can be disassembled into air (air dielectric constant ε _air = 1), dielectric one (dielectric constant recorded as ε ₁ ), medium two (dielectric constant ε ₂ ), and thicknesses are h _{air = ∞} , h ₁ , h _{2, respectively} . The calculation method is shown in equation (4).

In order to measure the full-load torque of the rotating shaft at 10%, it is necessary to perform experiments and simulations with a circuit formed by a capacitor of 5pF and an inductance of 1.6μH. The design result is that the size of the capacitor is 30mm and the number of turns is 3 ~ 4 The outer reading inductance is 44mm and the number of turns is 2-3. The wires are all enameled wires with a wire diameter of 0.5mm. The simulation values are calculated using the mathematical software MAPLE, which is quite consistent with the measurement results.

As mentioned above, the wireless passive strain sensor of the present invention has the following advantages:

1. Wireless transmission: The reading inductance coil is supported by the outer coil support, which can be measured on the rotating shaft without tangling.

2. Small space requirement: The sensing end is composed of the sensing inductor and the inner coil bracket. It does not need to install a battery module, which effectively reduces the occupied space.

3. Easy to operate: no tedious operations such as battery module replacement and shaft removal.

4. The shaft does not need to be processed: the shaft does not need to be lengthened, changed in material or shape.

5. Patch flexibility: can be attached to the surface of moderately curved objects.

6. Can be measured immediately.

The above-mentioned embodiments are only for explaining the technical ideas and characteristics of the present invention. The purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. When the scope of the patent of the present invention cannot be limited, That is, any equivalent changes or modifications made in accordance with the spirit disclosed in the present invention should still be covered by the patent scope of the present invention.

Claims (9)

A wireless passive strain sensor is suitable for measuring the strain of a rotating shaft. The wireless passive strain sensor includes: an outer coil support, the rotating shaft passes through the outer coil support; a reading inductance coil, a It is wound on the outer coil bracket; a capacitor patch is arranged on the rotating shaft, the capacitor patch is a flexible patch; an inner coil bracket is located inside the outer coil bracket, and the inner side The coil support is sleeved on the rotating shaft; a sensing inductor is wound around the inner coil support, and the sensing inductor is connected to the capacitor patch. The wireless passive strain sensor according to item 1 of the patent application scope, wherein the read inductor is connected to an antenna analyzer. The wireless passive strain sensor according to item 2 of the scope of the patent application, wherein the antenna analyzer scans the read inductor coil corresponding to a resonant frequency of the sense inductor coil. The wireless passive strain sensor according to item 3 of the patent application scope, wherein the antenna analyzer is connected to a computer, the computer receives the resonance frequency, and generates a resonance frequency result according to the resonance frequency, and displays the resonance Frequency results. The wireless passive strain sensor according to item 1 of the scope of the patent application, wherein a bearing structure is provided between the outer coil support and the inner coil support. The wireless passive strain sensor according to item 5 of the patent application scope, wherein the bearing structure includes a plurality of ball bearings. The wireless passive strain sensor according to item 6 of the patent application scope, wherein the ball bearing is a polyoxymethylene plastic bearing. The wireless passive strain sensor according to item 1 of the patent application scope, wherein the capacitor patch is a finger-type capacitor, and one end of the finger-type capacitor is connected to one end of the sensing inductance coil, and the finger-shaped The other end of the capacitor is connected to the other end of the sensing inductor. The wireless passive strain sensor according to item 1 of the scope of the patent application, wherein the included angle between the capacitor patch and the axis of the rotating shaft is 45 degrees.